Steelers2424

I was out running my revo today on flat pavement, and at one point the engine would rev but the truck would not move.
Once i got up close i hit the throttle and noticed the flywheel was spinning but the clutch bell was not.
I know it sounds like it is the clutch/shoes but i have a 3-shoe (buku) clutch and i cant image all three shoes broke at the same time. I pulled the engine out did not open anything up yet but looked at the shoes through the holes in clutch bell and everything looks to be in place.
I’m wondering if i did not rev it enough to engage the clutch shoes as i did not want to over rev with no load on the engine.

With the engine out i turned the spur gear by hand (counter clock wise) while holding the truck down so the wheels would not spin and there was some resistance but i could keep turning it. The resistance would build but it would free up at a certain point and build up again and free up again and repeat. It felt similar to turning your flywheel by hand where the resistance builds as the piston approaches the top and eventually frees up when its on its way down. The spur gear is not slipping either as i was watching for that.

ny ideas on what the issue could be here?

Steelers2424

i just checked out the clutch and it looks like some grease got into the clutch bell either from the bearings although i did clean them out or maybe from the purple stuff that goes into the buku cap. I sometimes do notice a little comes out after the first run if i just changed it out.
Regardless is this enough for it rev like it is in neutral? I was going to post a photo but does not even allow me to post a link to one.

Also would like to know what others thought about what i described in my original post regarding the spur gear, thanks again

Roelof

Leave the body off, start the engine, give some throttle and see what is rotating and what is not.

fyrstormer

iTrader: (1)

Clutch bell bearings always leak eventually. It's a side effect of having the entire bearing spinning at tens of thousands of RPMs, instead of the outer race being stationary as is the case with bearings elsewhere in the vehicle. I run Boca Yellow Seal ceramic bearings in my clutches, so I can open the inner bearing and spray out all the grease prior to installing. Even running dry, ceramic bearings last a long time, and it prevents contaminating the clutch shoes.

Unfortunately, I think if you get grease on the Aramid fiber pads that Buku clutches use, you have to replace the shoes entirely, because you'll never get all the grease out of them. Make sure to thoroughly degrease the clutch bell before reusing it, don't just wipe it off; even an invisible coating of grease can totally screw-up the engagement of the clutch shoes.

Regarding the spur gear's strange behavior, I think a transmission rebuild is in-order. Take it apart and see what's going on.

Maxximize

With the trans issue it sounds like you blew the primary gear in there. I have completely shredded those on my T Maxx before. Sometimes they will lose a few teeth and do exactly as you described.

I'm unfamiliar with Buku clutches, but I like to run aluminum shoes on all y trucks. Grease and/or fuel that gets in them simply burns off. I'm not sure if you can use any with the Buku set up though. My old .15 T Maxx used to run an Integy set up, actually really nice and uses 3 shoes. The big block Maxx runs an HPI Savage kit (17T bell?) with aluminum shoes on a 40T Revo spur, might also be Integy but I'm not sure.

fyrstormer

iTrader: (1)

I tried aluminum shoes once. Didn't like them. They grabbed too hard. My trucks are often called-upon to climb over curbs or other obstacles, and having shoes that can slip for several seconds without leaving debris welded to the inside of the clutch bell is a must-have. All but one of my nitro vehicles run Teflon shoes (which is easy to do because all but one are HPI, and HPI makes very good Teflon shoes); the exception is my T-Maxx Classic, which uses a Buku clutch with Aramid "Komposite" shoes. They slip without galling to the clutch bell just as well as Teflon, while still offering enough bite that the T-Maxx can wheelie (sometimes) with just a TRX2.5R engine.

I might run aluminum shoes in a car intended for on-road or racetrack use, to get harder launches, but for general off-road use Teflon or Aramid are perfect.

Buku *does* offer aluminum shoes if you really want them, though, and for a vehicle like the old T-Maxx, which has a centrifugal engagement mechanism inside the transmission, the ability to fine-tune the spring tension on each clutch shoe is a lifesaver. My T-Maxx can actually takeoff smoothly, which is something old T-Maxxes are *not* known for. It might work as well with a Buku clutch with aluminum shoes, I dunno, I haven't tried them myself.

- - -

Regarding the gearbox internals: I know they say not to grease the gears, but I did anyway. I very, very carefully applied a tiny amount of marine grease to each tooth, meshed them together, and wiped off the excess that was squeezed out from between the teeth. That way there's at least *something* keeping the plastic gear teeth from rubbing together too hard, overheating, and wearing down. I also adjusted the slipper clutch so it absorbs the shift-shock when second gear engages, so the truck doesn't jerk forward when the transmission shifts; this goes a long way to protecting the plastic gears from breaking teeth. It can still wheelie with the slipper clutch set this way, so you don't lose any of the "fun" factor.

Steelers2424

Thanks for the replies, i am going to switch the clutch out to a m2c one that i have, I will eventually purchase new buku shoes and clutchbell.
I will also open up the trans after work today to see if i can find any damage.

Thanks again

Roelof

Also be sure the shoes in the clutch do move when you put a screwdriver under them and fall back when you take away the screwdriver. Tolerances in size can lock up the shoes.

fyrstormer

iTrader: (1)

True.

Steelers2424

i opeedn up the trans and found some metal shavings in their not sure where they came from. There was also a small metal pin sitting in the case not sure where that came from either.

I know their are a few pins throughout the trans but they are held in either with a bearing or a metal clip and i believe all mine are in place. None of the gears look worn to me so im not sure what exactly the issue is with the trans

Anyone know how many posts you need in order to post link to photo's? I would like to post a few for those that are helping out with this issue.

any ideas? thanks again

Steelers2424

here is a photo, thanks again

Steelers2424

found the problem, it was the screw pin that broke on the forward-only shaft (5394X)

thanks again

Steelers2424

Anyone know the part number for the screw pin? I only see them as part of the forward only kit but not by themselves?